1. Technical Field
The present invention relates to a cleaning solution composition for a solar cell. More specifically, the present invention relates to a cleaning solution composition for a silicon wafer used to manufacture a solar cell.
This application claims the benefit of Korean Patent Application No. 10-2009-0056543, filed on Jun. 24, 2009, which is hereby incorporated by reference in its entirety into this application.
2. Description of the Related Art
Silicon solar cells are classified into monocrystalline silicon solar batteries, polycrystalline silicon solar batteries and amorphous silicon solar batteries.
A method of manufacturing a silicon solar cell is described as follows. In the case of a monocrystalline silicon solar cell, first, a monocrystalline ingot formed by a crystal pulling method is cut into sheets. A sawing tool may be a wire saw. Subsequently, the sheets are processed to a thickness of 100˜200 μm to form a wafer. Subsequently, a p-n junction layer, electrodes, a protective film and the like are sequentially formed on the wafer, thereby completing a monocrystalline silicon solar cell. Further, in the case of a polycrystalline silicon solar cell, molten silicon prepared by casting is cooled and crystallized to form a polycrystalline silicon ingot. Subsequently, the polycrystalline silicon ingot is cut into sheets. Subsequently, the sheets are processed to a thickness of 100˜200 μm to form a wafer. Subsequently, a p-n junction layer, electrodes, a protective film and the like are sequentially formed on the wafer, thereby completing a polycrystalline silicon solar cell.
In the method of manufacturing a silicon solar cell, in order to prevent the damage of the cut surface of the ingot and to decrease the reflectance of the cut surface thereof during the sawing process, a texturing process wherein the cut surface thereof is made uneven using a basic or acidic solution may be conducted. However, during the texturing process, the cut surface of the ingot may not be uniformly textured by the sawing oil or lubricating oil used in the sawing process, organic pollutants such as fingerprints and the like, glove prints or particulate pollutants occurring during the process of being handled by a worker, and belt prints transferred from conveyor belts. When the cut surface of the ingot is not uniformly textured, the yield of manufacturing solar batteries decreases rapidly, thus decreases the processability.
Therefore, in the solar cell manufacturing industry, RCA cleaning, which is used in semiconductor cleaning, was introduced in order to solve the problems related to organic pollutants, particulate pollutants and the like. More specifically, in the solar cell manufacturing industry, only SC-1 (SPM, hydrogen peroxide: ammonia: pure water) was introduced into the initial cleaning of solar cell wafer during RCA cleaning, or RCA cleaning was directly applied to the entire texturing process. However, when SC-1 cleaning or RCA cleaning is used, it is difficult to remove pollutants that are not particles. Further, when SC-1 cleaning or RCA cleaning is used, processing costs are increased because a solar cell manufacturing process needs additional processes. Further, when SC-1 cleaning or RCA cleaning is used, it is difficult to conduct work because the process temperature is 70˜100° C.
Accordingly, various attempts to overcome the problems of SC-1 cleaning or RCA cleaning have been made. For example, Korean Unexamined Patent Application Publication No. 2007-0023954 discloses a method of cleaning a substrate using ozone water instead of hydrogen peroxide in the SC-1 solution. This method is advantageous in that the effects of removing organic pollutants can be improved because ozone water, which is an oxidant that is not harmful to the environment and is stronger than hydrogen peroxide, is used. However, this method is problematic in that the process temperature for SC-1 cleaning must be maintained constant, and an ozone generator must be additionally provided. Further, Japanese Unexamined Patent Application Publication No. H05-275405 and Japanese Unexamined Patent Application Publication No. 2003-221600 disclose a detergent solution prepared by adding a complexing agent such as a phosphonate compound or a condensed phosphate compound to an SC-1 solution or adding an ethylene oxide-added surfactant or complexing agent to the SC-1 solution. This detergent solution can remove metal particles, but cannot efficiently remove organic pollutants, particulate pollutants and pollutants attributable to equipment. Further, Korean Unexamined Patent Application Publication No. 2005-0103953 discloses a semiconductor cleaning solution composition essentially comprising quaternary ammonium hydroxide and a specific surfactant. However, the semiconductor cleaning solution composition is problematic in that the performance of removing fat or particulate pollutants is not excellent.